This invention relates to a hand-held flashlight and in particular to a flexible core for connecting the power generating end of the flashlight to the power using end thereof.
The modern flashlight is one of the most useful implements found in the home, automobile, or other locations whereat it is desirable to have a portable source of illumination. Very often, the flashlight is employed in situations whereat it is desirable that the user's hands be free to hold or maneuver an object being illuminated.
For example, when a person is performing maintenance on an automobile, there are many instances when the use of both hands to perform a maintenance task is desirable even though artificial illumination is still needed. Other such applications include reviewing documents, as for example reading maps in a car, attempting to find an object in a relatively dark location, and performing similar tasks. When the user has a standard flashlight, the user must resort to various unorthodox means for holding the flashlight to free up his or her hands. For example, the user may place the flashlight under an arm, in a mouth, or rest the flashlight on a nearby support which may not necessarily be sufficiently close to the object being viewed to provide the desired illumination.
Heretofore there have been a variety of lighting products that have included flexible cores for the general purpose of manipulating a light source into a desired position. In some cases, the light source is in a base and a flexible core contains glass fibers to conduct the light to the tip of the core. Some of these lighting products are battery powered, while most are AC powered to provide the high intensity light generally needed for such applications as inspection work.
In other cases, the light may be constructed with a gooseneck formed from strip wound, interlocked, flexible metal tubing. Generally, such a lighting product is used for AC powered lamps such as desk lighting and includes two wires internally carried by the flexible metal tubing. In some battery powered applications, one of the wire conductors may be omitted and the second conductive path is provided by the flexible metal tubing itself.
There are several other lighting products, some of which are battery powered and others of which are AC powered, that utilize a flexible core constructed from a plastic jacket and coaxial cable. The center core is usually a solid wire. It is separated by a plastic insulator, around which is wrapped a braided metal wire sheathing. The plastic jacket, typically a polyvinyl chloride, shields the exterior. Other lights having a flexible core use a series of copper, lead, or aluminum solid wire, that are either individual or stranded together to provide physical support for the flexible core. In some instances, the wire or wires are used as conductors, to provide one or more of the two required electrical paths for a light source. In some applications, the wires are bare and in others the wires may be individually or collectively insulated with some plastic sleeving
Further, there are several known AC powered lights that utilize a series of interlocking plastic elements to form a flexible core. This core is sold under brand names such as "LockWood" and "Cederburg." The flexible core was developed to carry cutting/cooling fluid to work pieces supported on metal cutting machines such as lathes and milling machines. The flexible core is generally hollow, and is leak tight. The core is flexible to allow the fluid to be directed onto various work pieces as needed. AC powered lights utilizing this flexible core generally have two insulated wires running inside the center hole formed by the flexible plastic elements.
The main problem with cores utilizing the common gooseneck strip wound, interlocked flexible metal tubing is that the bend radius is too limited for a flexible light application. Although the gooseneck tubing is reasonably durable, it also suffers from a gradual reduction in its ability to withstand a flexing force due to wear at the interlocking surfaces. The interlocking surfaces provide the requisite friction to make the product hold the shape into which the user has placed the core.
The main problem associated with the metal wire and/or coaxial cable types of cores is that they have a very limited flex life. The metal rapidly fatigues and, if bent back and forth continuously at the same location, the core will tend to break at that spot. In some instances, this can occur after only 100 bending cycles.
The core formed by a plurality of plastic interlocking elements offers the advantage of long life while bending back and forth. The core does not tend to fatigue, and due to the use of low friction coefficient materials, such as acetel plastic, the core elements tend to have relatively little wear. However, prior art plastic interlocking element cores tend to suffer from a few problems. Since each element is free to rotate relative to the next interlocked element, the whole chain of plastic elements can become skewed and kinked and thus fall out of alignment. This creates a very unattractive core. In addition, the elements are linked together by snapping each element together as a ball-joint socket to the next successive element. While the foregoing allows a relatively large amount of free movement and easy assembly/disassembly, such structure also allows the elements to separate from one another if the interlocked chain is bent into too tight a radius by a relatively strong applied force. Modifications to the socket design will increase the ability of the core to withstand forces that tend to cause socket separation.
One of the usual situations involving the need to have a "hands free" flashlight involves reading a map or similar document in an automobile. It is desirable to have a flashlight capable of being powered by a relatively few standard AA, C or D cells while also having the ability of being powered by the much higher level of DC voltage available from a standard automobile battery. For this application the relatively few cells is preferably two which will provide an average DC voltage of 2.4 volts. The higher DC voltage generated by the automobile battery must be converted to a lower working voltage level usable by a flashlight bulb, without excessive heat generation. Such voltage conversions may be accomplished with a DC convertor or pulse width modulation circuit or by the use of passive means, such as a dropping resistor.
The circuit approach has several basic drawbacks. The first is the relatively expensive cost associated with components and manufacture and the second is the problem of having to enclose the circuit board having the control within the flashlight. A third drawback is reliability due to the increased number of components and relatively harsh operating environment.
The dropping resistor on the other hand is inexpensive and reliable but creates excessive heat when dissipating the power produced in dropping the DC voltage from 12 volts to approximately 2.4 volts. This heat generation poses a packaging problem due to temperature limitations of the standard plastic materials employed in the manufacture of the flashlight housing.
Accordingly, it is an object of this invention to provide a flexible core for a flashlight or similar device which is capable of holding a user-defined shape, permits repetitive flexing and enables the power conducting means to pass through the core so that power supplied at one end of the core can be delivered to the other end which includes a power using element.
It is a further object of the invention to provide an adaptor for a flashlight or other similar device which will enable the device to be powered by standard dry cells or a 12 volt automotive battery.